Fuse for brushless exciter



Feb 17 1970 D. B. HoovER 3,496,510

FUSE FOR BRUSHLESS EXCITER Filed June 6, 1968 Dillon B. Hoover BY f.- n/.M

United States Patent O 3,496,510 FUSE FOR BRUSHLESS EXCITIER Dillon B. Hoover, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 6, 1968, Ser. No. 734,928 Int. Cl. H0111 85/04 U.S. Cl. 337-159 8 Claims ABSTRACT OF THE DISCLOSURE A fuse for mounting in a radial direction on a rotating shaft and subject to large centrifugal forces has the plugs at each end of the fuse tube in which the fuse element or elements are disposed secured against rotational movement about the longitudinal axis of the fuse tube by a plurality of peripherally spaced pins passing through the fuse tube into each of the fuse plugs. Additionally, at one end of the fuse tube an external extended portion of the plug is threaded and has a ring threaded onto the plug and firmly pressing against the adjacent end of the fuse tube. The fuse element is supported by and secured to an insulating plate extending axially through the fuse tube and into grooves in the inside surfaces of the plugs.

CROSS REFERENCE TO RELATED APPLICATIONS This application is related to the copending application of Bernard B. Winer et al. for Fusible Means for Rotating Electrical Device, Ser. No. 174,370, tiled Feb. 16, 1962 and assigned to the assignee of the instant invention.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to fuses for mounting in a radial direction on a rotating shaft and subjected to high centrifugal forces.

Description of the prior art In the early years of the brushless exciter art fuses were generally mounted with the axis of the fuse tube transverse to the axis of rotation of the shaft rather than extending radially from the axis of rotation of the shaft, and great difficulty was encountered because of centrifugal forces applied to the fuse element. A more satisfactory fuse suitable for mounting on a rotating shaft is that described in the aforementioned copending application in which a supporting plate of insulating material extends axially through the fuse tube, the fuse element is secured to the supporting plate at a number of positions thereon, and the fuse element has curves in it to provide flexibility in the face of centrifugal forces.

SUMMARY OF THE INVENTION A fuse for mounting on a rotating shaft extending in a radial direction has a fuse tube enclosing the fuse element which is secured to terminal plugs at each end of the fuse tube. The fuse tube is secured against rotary movement about the longitudinal axis thereof with respect to the plugs by pins extending through the fuse tube and into the plugs. Additionally at one end the plug has an extended threaded portion with a ring in threaded engagement thereon rmly pressing against the adjacent end of the fuse tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a view of a fuse for radial mounting according to the prior art described and claimed in the aforementioned copending patent application;

3,496,510 Patented Feb. 17, 1970 ice DESCRIPTION OF THE PREFERRED EMBODIMENT My invention may most easily be described with reference to the improvements which I have made in the fuse described and claimed in the aforementioned copending application of Winer et al., which fuse of the prior art is illustrated in FIGURE 1. The fusible device generally designated 12 comprises an insulating casing 16 formed of a suitable high strength material such as glass melamine and having end terminal connectors or plugs 17, 18 each having a terminal mounting hole therein, the hole in member 17 being shown at 17a. The terminal connector 18 may constitute a mounting lug which may be fxedly secured and connected to a conductive mounting block, not shown.

The fusible device 12 is mounted radially of the rotating shaft so that one or more parallel disposed fusible elements 23 is disposed radially of the rotating apparatus. The fusible element 23 is preferably provided with notches and holes, not shown in FIGURE 1, but which may be similar to those in FIGURE 2 illustrating my invention. In addition, the fuse link 23 is provided with preformed rivet holes 26. An insulating support strip 27 extends axially within the fuse tube 16 and has each end thereof extending into a notch or slot 28 provided in the end terminal plugs 17 and 18 and in addition insulating support strip 27 has rivet holes 29 which register with the rivet holes 26 of the fusible element or elements 23. Suitable rivets 30 are employed to fxedly secure the mid portions 23a of the 'fusible elements 23 to the supporting strips 27. While the fuse is mounted on a rotating shaft, the supporting strip 27 extends radially from the axis of rotation.

The rating and characteristics of the fusible device 12 are determined by the number and cross sectional area of the fusible elements 23 together with the disposition and size of the notches and holes therein, not shown. The fusible element 23 is preferably composed of a suitable conductive material such as silver, for example. The fusible element 23 is provided with flexible end portions 23h and 23C in this particular instance comprising two substantially right angle bends, thereby providing flexibility radially of the fusible element 23. An arc-quenching solid material, such as sand, lls the fuse casing 16.

Particular reference is made now to FIGURE 3, a fuse constructed according to my invention. A fuse tube 36 extends between end terminal connectors or plugs 37 and 38. The fuse tube 36 is composed of insulating material. End terminal 38 has peripherally spaced bores therein including bores 71 and 72, these being in alignment with peripherally spaced bores through the adjacent end of the fuse tube two of these being shown at 73 and 74. Pins pass through the bores in the fuse tube into the aligned bores in the end terminal connectors, two of these pins being shown at 75 and 76, and hold the end terminal connector against rotary movement with respect to the fuse tube 36.

The end terminal connector 37 at the bottom of the fusible device as seen in FIGURE 3 has a portion 78 thereof extending beyond the adjacent end of the fuse tube 36, the extended portion 78 being threaded at 79. In threaded engagement with the end terminal connector at 79 is a ring 80 preferably composed of metal which has the upper surface thereof 81 firmly pressing against the adjacent end of the fuse tube 36. The end terminal connector 37 also has peripherally spaced bores extending thereinto, two of these being shown at 91 and 92, in alignment with bores 93 and 94 passing through the fuse tube, in which are disposed pins 95 and 96.

A fusible element 43 extends axially through the fuse tube, the ends being very strongly secured to the end terminal connectors 37 and 38 to form excellent mechanical and electrical connection thereto. Fusible element 43 has flexible end portions 40 and 41. A supporting strip of insulating material 57 extends axially within the fuse tube and has each end thereof extending into a slot 5,8 in a terminal plate or plug. The fusible element 43 is firmly secured to the supporting strip of insulating material 57 as by rivets including 60 and 61 passing through aligned bores in the fusible element and the supporting strip.

The fusible device has an indicator apper 33, FIG- URE 4, preferably made from a resilient metallic material such for example as phosphorus bronze. It is secured at one end by a screw 31 within a slot of the terminal connector 38. The other end of the indicator 33 is secured to a fuse wire 32, FIGURE 3, of relatively high resistance which extend through the interior of the fuse casing 36 and is electrically connected and physically secured to the other end terminal plug 37. As is well known by those skilled in the art, rupture of the fuse link or links 23 will also result in immediate breaking of the fuse wire 32 and hence permissive flexing of the indicator 33 to the indicating position. Centrifugal forces may assist this indicating motion.

The remainder of the chamber 62 formed within the fuse casing between the end terminal connectors is filled with an arc-quenching material such as sand.

Particular reference is made now to FIGURE 2, a cross sectional view through the fuse of my invention in a plane rotated at 90 with respect to the plane in which the cross section of FIGURE 3 is taken. Fusible element 43 has transverse extending axially spaced rows of holes 64, 65 and 66 therein with adjacent notches 67, 68 and 69 on each edge of the fusible element. The aforementioned, fusible element 43 is seen to have four holes therein for the passage of rivets to secure the fusible element to the supporting strip 57, these rivet holes being shown at 46. It is understood that the ends 44 and 45 of the fusible element extend into slots 51 and 52 in the terminal connectors 38 and 37, FIG. 3, making good mechanical and electrical connection therewith. Four rivets, not shown, pass through the holes 46 in the fusible element, pass through aligned holes or bores in the supporting insulating plate, and secure the two firmly together, and it is understood that the supporting plate shown in FIGURE 3 at 57 extends into slots 58 in the terminal plugs. The supporting plate extends axially of the fuse tube but extends radially from the rotating shaft while the fuse is mounted thereon. In the rotated sectional view pins 75a, 76a, 95a and 96a are seen extending through slots in the fuse tube and into aligned bores in the terminal connectors.

As in FIGURE 3, the ring 80 is securely threaded to the terminal connector 37 and firmly presses against the adjacent end of the fuse tube 36.

Further summarizing the advantages of my invention, as previously stated fuses for brushless exciters must be capable of withstanding the mechanical forces incident to high speed rotation. The larger the diameter of the fuse wheel on which the fuses are mounted and `the farther they are mounted from the axis of rotation, the greater the centrifugal force on the fuse and the elements inside. My invention is especially suitable for preventing failure of the fuse casing at or near the ends thereof where they come in Contact with the end terminal connectors.

I thread a nut or ring on the extended end of one terminal connector 37 so that it bears solidly against the end of the casing or fuse tube. This distributes the stresses so that the Whole cross section of the casing or fuse tube is loaded in an approximately uniform manner. Further I provide peripherally spaced pins extending through the fuse tube near the ends thereof and extending into aligned bores in the adjacent end terminal connectors.

The aforegoing written description and the drawings are illustrative and exemplary only and should not be interpreted in a limiting sense.

I claim as my invention:

1. A current limiting cell fuse for a rotating rectifier comprising in combination: a tubular casing composed of insulating material; a pair of terminal plugs fitted into the ends of said casing, the casing having two rows of peripherally spaced radially extending bores therearound near the ends thereof respectively, the terminal plugs having therein peripherally spaced bores in alignment with the bores in the casing respectively; a plurality of pins extending through the bores in the casing and into the bores in the terminal plugs and securing the casing against rotary movement with respect to the terminal plugs; one of said terminal plugs having a extended cylindrical portion extending beyond the adjacent end of the tubular casing, said portion being externally threaded; a ring threaded onto said last-named terminal plug and firmly abutting against the adjacent end of the tubular casing; each of the terminal plugs having on the axially inner surface thereof at least one pair of spaced parallel grooves; an insulating plate arranged inside said casing in a direction longitudinally thereof and having axially outer ends each projecting into one of said pair of grooves; a ribbon fuse link arranged inside of said casing exceeding in length the spacing between said axially inner surface of each of said pair of plugs, said link projecting with each of the axially outer ends thereof into another of said pair of grooves, and said link including a portion of reduced cross section situated between said axially outer ends thereof, bent out of the plane defined by said axially outer ends thereof into the plane defined by said plate and in abutting relation with said plate; and fastener means projecting through said portion of said link and through said plate and securing said portion of said link to said plate.

2. A fusible device adapted for rotating equipment comprising an insulating tubular casing and spaced terminal connectors closing the ends thereof, said terminal connectors extending into said casing, the casing having two rows of peripherally spaced bores therethrough near the ends thereof, the terminal connectors having peripherally spaced bores therein in alignment with the bores in the casing, a plurality of pins passing through the bores in the casing and into the bores in the terminal connectors and holding the casing against rotary movement with respect to the terminal connectors, one of said terminal connectors extending beyond the adjacent end of the casing and having the external surface thereof threaded, a ring threaded onto said extended portion and firmly abutting against the adjacent end of the tubular casing, at least one fuse element disposed internally of the fuse casing and interconnecting the end terminal connectors thereof, and in insulating support strip disposed longitudinally of the tubular fuse casing and secured to the fuse element.

3. The combination as set forth in claim 2 wherein an additional indicator fuse wire and an indicating flapper disposed adjacent the external surface of one terminal connector are provided for fuse indication.

4. The combination in a rotatable fuse of a tubular fuse casing having a pair of spaced terminal connectors closing the ends thereof, the tubular fuse casing having two rows of peripherally spaced radially extending bores therethrough near the ends thereof, the terminal connectors having peripherally spaced bores extending thereinto in alignment with the bores in the fuse casing, a plurality of pins extending through the bores in the fuse casing and into the bores in the terminal connectors and securing the fuse casing to the terminal connectors, one of the terminal connectors having a portion extending beyond the adjacent end of the fuse casing, said portion being threaded on the external surface thereof, a ring threaded thereon and firmly abutting against the adjacent end of the fuse casing, fusible means interconnecting the spaced end terminal connectors comprising a plurality of fusible elements, and an insulating support strip secured to the mid portion of each fusible element.

5. The combination according to claim 4 wherein the insulating support strip is disposed to the side of the fusible element nearest the inner surface of the fuse casing.

6. The combination of claim 2 wherein exibility in the fuse element is provided adjacent the ends of the support strip.

7. The combination of claim 6 wherein the flexibility is provided by two right angle bends at the ends of each fuse element.

8. In a fusible device adapted to be subjected to large centrifugal forces, in combination, a pair of spaced terminal connectors adapted to be connected in an electrical circuit and adapted to have a fuse element extend therebetween and a tubular fuse casing composed of insulating material extending between the spaced terminal connectors, each of the spaced terminal connectors extending into the fuse casing, the fuse casing having rows of peripherally spaced radially extending bores around the ends thereof, the terminal connectors having rows of peripherally spaced bores therein in alignment with the bores in the fuse casing, a plurality of pins extending through the bores in the fuse casing into the bores in the terminal connectors and securing the fuse casing to the terminal connectors, one of the terminal connectors having a portion extending beyond the adjacent end of the fuse casing, said portion being externally threaded, and a ring threaded onto said portion and firmly abutting against the adjacent end of the tubular fuse casing.

References Cited UNITED STATES PATENTS 1,925,060 8/ 1933 Stephenson 337-25 X 2,166,174 7/1939 Popp 337-234 2,644,872 7/1953 Laing 337-234 BERNARD A. GILHEANY, Primary Examiner H. B. GILso, Assistant Examiner U.S. Cl. X.R. 337-231 

